Editor’s pick&colon; Less a snowball, more of a slushball

From
Birger Johansson

Richard Webb describes the most extreme version of a “snowball Earth” event, as proposed by Joseph Kirschvink (18 July, p 28). Others have suggested milder “slushball Earth” events. Since life apparently bounced back quickly after each event, it must have found some refugia.

Research by Adam Campbell at the University of Washington, Seattle, indicates that simple photosynthetic algae could have survived in a narrow body of water with characteristics similar to today’s Red Sea. The “hard snowball” interpretation – with equatorial temperatures of -50 °C lasting tens of millions of years – would rule that out. So where did life hide out? Hibernation fails on time scales beyond millennia. Crater lakes may be warm, but no single volcano survives that long. Very salty lakes might remain liquid but will kill everything except extremophiles. Even organisms living at sea floor hot vents need oxygen, dissolved at the liquid surface. Yet we exist.